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8.07471

Sigma-Aldrich

Polyphosphoric acid

for synthesis

Synonym(s):

Polyphosphoric acid, PPA

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About This Item

Linear Formula:
HO[P(OH)(O)O](n)H
CAS Number:
8017-16-1
MDL number:
MFCD00084480
UNSPSC Code:
12352301
EC Index Number:
232-417-0
NACRES:
NA.22

vapor pressure

2 hPa ( 20 °C)

Quality Level

200

Assay

83-87% P2O5 basis (acidimetric)

form

viscous liquid

bp

530 °C/1013 hPa

mp

-20 °C

density

2.06 g/cm3 at 20 °C

storage temp.

2-30°C

InChI

1S/O5P2.H3O4P/c1-2-7-4-3-6(1)5-7;1-5(2,3)4/h;(H3,1,2,3,4)

InChI key

FVYIVXLIMHNYTD-UHFFFAOYSA-N

General description

Polyphosphoric acid (PPA) is a strong mineral acid that combines orthophosphoric acid and linear phosphoric acids. It is widely used in organic synthesis because of its powerful dehydrating properties, low nucleophilicity of the phosphoric acid media, good solvation power, relatively mild acidity, and low oxidation potential. Even though PPA is a significantly weaker acid than H2SO4, it demonstrates 100% dehydration rate.

Application

Polyphosphoric acid (PPA) can be used as a reagent:
  • In acylation and alkylation reactions.
  • To synthesize cyclic aromatic compounds via cyclization of aromatic acids, esters, ketones, aldehydes, acetals, alcohols, and alkenes.
  • In Bischler−Napieralski reaction to construct isoquinoline ring system from phenethylformamides.
  • To prepare substituted indoles at position-2 from hydrazones via Fisher indole synthesis.
  • For the conversion of oximes into amides via Beckmann rearrangement.

PPA can also be used as a catalyst to synthesize:
  • Aniline derivatives by Lossen rearrangement of aromatic carboxylic acids with nitromethane.
  • Amides by hydrolysis nitriles.
  • Dimethyl carbonate (DMC) from urea and methanol.
  • Benzofurans by cyclization of α-phenoxy ketones.

PPA is also used with other reagents for various organic transformations. For example:
  • PPA/Ethanethiol mixture can be used to selectively open one epoxide in bis-epoxy steroid.
  • PPA/POCl3 catalytic mixture used to convert tertiary alcohols into corresponding chlorides.
  • PPA/acetic acid is used to synthesize nonenolizable β-diketones.
  • PPA/potassium iodide mixture used to convert primary methyl ether to a primary alkyl iodide.
  • PPA/nitric acid catalytic combination used for nitration reactions which is less hazardous than Ac2O/HNO3 mixtures.

Analysis Note

Assay (acidimetric, calc. as P₂O₅): 83.0 - 87.0 %
Due to its specific melting range the product may be solid, liquid, a solidified melt or a supercooled melt.

Pictograms

Corrosion
GHS05

Signal Word

Danger

Hazard Statements

H290 - H314

Hazard Classifications

Eye Dam. 1 - Met. Corr. 1 - Skin Corr. 1B

Storage Class Code

8B - Non-combustible, corrosive hazardous materials

WGK

WGK 1

Flash Point(F)

does not flash

Flash Point(C)

does not flash

Certificates of Analysis (COA)

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Synthesis of dimethyl carbonate from urea and methanol using polyphosphoric acid as catalyst
Sun Jianjun, et al.
J. Mol. Catal. A: Chem., 239(1-2), 82-86 (2005)
Polyphosphoric Acid
Dodd, John H
eEROS (Encyclopedia of Reagents for Organic Synthesis) (2001)

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